1. Field of the Invention
The present invention generally relates to a surgical stapling instrument for applying surgical staples to tissue and, more particularly, to a surgical stapling instrument for performing a circular anastomosis stapling operation. More specifically, this invention relates to a surgical instrument in which a stapling head assembly is mounted by a flexible shaft to an actuator handle assembly and to an improved actuator mechanism for transmitting the required operating forces and movements from the actuator handle assembly through the flexible shaft to the stapling head assembly. Also, this invention relates to an improved stapling head assembly which reduces the operating forces required to perform the tissue stapling and cutting operations. Further, this invention concerns an improved actuator mechanism which controls the opening and closing of the stapling head assembly and adjustment of the anvil gap to produce a desired staple height.
2. Description of the Prior Art
The field of surgical stapling has seen substantial advances in the past decades. Specifically, in the area of internal anastomotic stapling the advances have been quite dramatic. Devices such as the Proximate.TM. ILS stapler, produced by the assignee of the present invention, Ethicon, Inc., Somerville, N.J., have enabled surgeons to perform operations and procedures which were heretofore perceived as difficult, if not impossible, with relative ease.
Generally, in the performance of a surgical anastomotic stapling operation, two pieces of lumen or tubular tissue, e.g., intestinal tissue, are attached together by a ring of staples. The two pieces of tubular tissue may be attached end to end or one piece of tubular tissue may be attached laterally around an opening formed in the side of another piece of tubular tissue. In performing the anastomosis with a stapling instrument, the two pieces of tubular tissue are clamped together between an anvil provided with a circular array of staple forming grooves and a staple holder provided with a plurality of staple receiving slots arranged in a circular array in which the staples are received. A staple pusher is advanced to drive the staples into the tissue and form the staples against the anvil. Also, a circular knife is advanced to cut the excess tissue clamped between the anvil and the staple holder. As a result, a donut-shaped section of tissue is severed from each lumen and remains on the anvil shaft. The tubular tissue joined by the circular ring of staples is unclamped by advancing the anvil shaft distally to move the anvil away from the staple holder. The stapling instrument is removed by pulling the anvil through the circular opening between the pieces of tubular tissue attached by the ring of staples.
In the prior art, several types of circular anastomosis stapling instruments are known. For example, U.S. Pat. Nos. 4,576,167 and 4,646,745 to Noiles disclose a surgical stapler in which a stapling assembly is connected by an elongated shaft assembly having a longitudinally curved section to an actuator assembly. The shaft assembly includes an articulated hollow tube and a flexible band inside the tube, which are coaxial with a curved section of a hollow support shaft, for transmitting the compression and tension forces required to operate the stapling assembly.
It is also known in the prior art to provide a circular anastomosis stapling instrument including a flexible shaft which allows the stapling head to assume various orientations relative to the actuator assembly. Examples of circular stapling instruments with flexible shafts are disclosed in Noiles et al U.S. Pat. No. 4,473,077, Barker et al U.S. Pat. Nos. 4,671,445 and 4,754,909, Shichman U.S. Pat. No. 4,488,523, Swiggett U.S. Pat. No. 4,485,817 and Hervas U.S. Pat. No. 4,962,877.
Noiles et al U.S. Pat. No. 4,473,077 discloses a surgical stapling instrument including a stapling assembly and an actuator assembly connected by a longitudinal shaft assembly with a longitudinally flexible section. The flexible shaft section comprises an inner tube assembly including a plurality of washer-shaped segments, an outer tube assembly comprising a plurality of washer-shaped segments, and an outer elastic sheath. Inside the inner tube assembly is an actuator band for transmitting tension from the actuator assembly to the stapling assembly. The washer-shaped segments of each tube assembly provide lines of contact with the adjacent segments which allow the segments to pivot with respect to each other as the shaft assembly is deformed into a curve. The design of washer-shaped segments limits the bending of the shaft assembly to motion in a single plane, i.e., bending up or down in a vertical plane.
Barker et al U.S. Pat. No. 4,671,445 discloses a flexible surgical stapler assembly including a staple firing head assembly and a handle actuator assembly connected together by a flexible spine. The spine consists of a series of spine segments each having a hemispherically-shaped concave recess which mates with a hemispherically-shaped forward surface of the adjacent spine segment. A cable extends longitudinally through the spine segments from the handle actuator assembly to the staple firing head assembly. The spine segments abut one another and extend between the handle actuator assembly and the stapling head assembly and translate a force which maintains that portion of the staple firing head assembly to which the forwardmost spine segment abuts in a fixed position relative to the cable.
Barker et al U.S. Pat. No. 4,754,909 discloses a flexible stapler including a plurality of rigid spine segments having opposed concave and convex surfaces. The spine segments are disposed in end to end relationship to form a spine structure for connecting an actuator assembly to a stapling head assembly. A flexible stiffening assembly extends through aligned openings in the spine segments. The stapler includes tension applying means having a disengaged position at which sufficient slack is provided in the stiffening assembly to afford flexing of the spine structure to orient the spine segments and thereby the head assembly at a desired orientation relative to the actuator assembly and an engaged position at which tension is applied to the stiffening assembly to compress the spine segments and rigidify the spine structure.
Shichman U.S. Pat. No. 4,488,523 discloses a surgical stapler apparatus comprising an applicator portion and an actuator portion connected by a transversely flexible shaft. The flexible shaft contains a hydraulic line for connecting fluid chambers in the applicator and actuator portions. The hydraulic line is shaped as a helix and housed in a cylindrical sheath of flexible material.
Swiggett U.S. Pat. No. 4,485,817 discloses a hydraulically operable surgical stapler including a longitudinally flexible shaft for connecting the stapling section to the actuator section. The flexible shaft includes a first, flexible, small-diameter tube for transmitting hydraulic pressure contained in a stiffer, but flexible, second tube which gives the shaft the relatively slight degree of rigidity necessary to enable the flexible shaft to maintain a desired shape into which the shaft has been bent. The first and second tubes are contained in an outer sleeve which is secured to the stapling section and to the acutator section.
Hervas U.S. Pat. No. 4,962,877 discloses a hydraulic device including a flexible body for performing a surgical anastomosis. The body consists of three flexible hydraulic connecting tubes which are covered by a flexible plastic tube.
European Patent Application No. 293,123-A2 discloses a surgical anastomosis stapling apparatus including a stapling assembly comprising a tubular housing which supports an annular array of staples, a staple pusher mounted for movement between a retracted position within the housing and an extended position for expelling the annular array of staples, and a cylinder slidably mounted within the pusher assembly for selectively mounting either a trocar or an anvil assembly. The cylinder includes a central bore at its distal end for receiving a solid anvil shaft which is releasably held in the central bore by a detent formed on a spring member mounted at the distal end of the cylinder. The anvil shaft includes external longitudinal splines which engage internal splines provided within the housing for aligning the anvil shaft with the housing.
Co-pending U.S. application Ser. No. 590,404, filed Sep. 28, 1990, by Main and assigned to Ethicon, Inc., now U.S. Pat. No. 5,104,025, discloses a surgical stapling device including an anvil portion which is detachable from a stapling head portion containing a trocar tip upon which the anvil is attached. The anvil portion contains an elongated sleeve with an opening through which the trocar tip is inserted. The anvil is provided with a locking clip which releasably engages an indentation or ridge provided on the trocar tip which allows the anvil to be separated from the trocar tip.